Surface Interface Regulation Of SrTiO₃ For Photocatalytic Reduction Of CO₂

Converting CO₂ into highly value-added carbon-based fuels over photocatalysts is an ideal pathway to reduce atmospheric CO₂ concentrations and achieve carbon neutrality.However,low yields and complex products are two major problems facing industrial applications.On the one hand,easy recombination of electrons and holes over semiconductors severely limits the photocatalytic performance.On the other hand,diverse products could be obtained during the CO₂reduction process due to multiple electron transfers,thus leading to difficulty in separation of different products.Therefore,it is of great significance to achieve efficient CO₂ photoreduction with highly selective production.As a typical perovskite structure compound,SrTiO₃ is expected to achieve further development and application due to its simple access and better performance.Therefore,this paper aims to develop highly efficient SrTiO₃-based nano-photocatalysts and reveal the main factors influencing the product selectivity during the CO₂ reduction reaction.By the use of crystallographic surface modulation and co-catalyst loading,charge transport and separation,molecular adsorption and proton supply are optimized.The main studies and conclusions of this thesis are as follows.（1）SrTiO₃ nanoparticles with adjustable ratios of（001）and（110）crystalline surfaces were synthesized by a hydrothermal method using 1,2propanediol as surfactant.Intrinsic relationship between the crystalline surface structure and its CO₂ reduction product selectivity was investigated.Experiments and theoretical calculations show that the CO₂ reduction reaction pathway is CO₂→*COOH→CO→*CH_x→CH₄.CO₂ reduction.（001）and（110）crystal planes exhibit different product selectivity with CO and CH₄ dominating respectively.When（001）crystal plane is the main exposed crystal plane,the electric field effect between the two crystal planes can induce the migration of photo-generated electrons and holes of SrTiO₃ to the（001）and（110）crystal planes.The spatially separated hole oxidation and electron reduction reactions enhance the CO₂conversion efficiency.（110）surface has lower active charge transfer resistance and higher density of electronic states corresponding to the valence band.These properties promote further improvement of CO₂ reduction efficiency.Anisotropic SrTiO₃ has strong CO adsorption capacity,which can promote the generated CO continue to be adsorbed on the surface.It means that CO can participate in the subsequent hydrogenation reactions to generate*CH_x species.Eventually,the selectivity of CH₄ products raises up to a ratio of 72.59%.The results confirm that the product of CO₂ reduction by SrTiO₃ depends on the chemistry of its crystalline surface,which has less correlation with the concentration of photogenerated carriers on its surface.（2）Loaded Pt nanoparticle dioctahedral SrTiO₃ was constructed under the action of the electric field at the crystal plane.Directional modification of Pt was successfully achieved by exploiting the electron transfer to the（001）crystal plane.Microscopic morphological observation by SEM and TEM confirmed that Pt nanoparticles were in close contact with the surface of SrTiO₃（001）,which facilitated the further transport of photogenerated electrons to Pt after carrier excitation.The constructed Schottky junction can increase the surface charge density while suppressing the photogenerated charge complex.Photoelectric tests have verified that this particular structure can indeed reduce the hindrance in electron transfer and accelerate the kinetics of the photocatalytic reaction.Thus,combining the advantages of crystallographic surface engineering and the Schottky structure,selectivity of CO₂ reduction for 0.05 Pt/TSTO is significantly altered compared to pre-loading,with the highest selectivity for CO₂ to CH₄conversion.Although the introduction of CO₃O₄ theoretically accelerates the water oxidation reaction and increases the proton supply level,the experimental results demonstrate that its CO₂reduction product selectivity is not transformed.Based on these facts,it is proposed that adsorption properties on the catalyst surface during the conversion of CO₂ to CH₄ has a greater influence on the reaction process compared to the proton concentration.This study provides a feasible method for the product modulation of co-catalyst-assisted SrTiO₃-based photocatalysis in the direction of CO₂ reduction.